#include <iostream>
#include <vector>
using namespace std;

struct ListNode
{
    int val;
    ListNode *next;
    ListNode() : val(0), next(NULL) {}
    ListNode(int x) : val(x), next(NULL) {}
    ListNode(int x, ListNode *next) : val(x), next(next) {}
};
class Solution
{
public:
    ListNode *ZZZ(ListNode *head)
    {
        ListNode ret(0, head), *tail = &ret;
        while (tail && tail->next)
        {
            ListNode *cur = tail->next;
            ListNode *next = cur->next;
            if (next && cur->val == next->val)
            {
                while (next && cur->val == next->val)
                    next = next->next;
                tail->next = next;
            }
            else
            {
                tail->next = cur;
                tail = tail->next;
            }
        }
        return ret.next;
    }
};
ListNode *createByTail()
{
    ListNode *head;
    ListNode *p1, *p2{};
    int n = 0, num;
    int len;
    cin >> len;
    head = NULL;
    while (n < len && cin >> num)
    {
        p1 = new ListNode(num);
        n = n + 1;
        if (n == 1)
            head = p1;
        else
            p2->next = p1;
        p2 = p1;
    }
    return head;
}
void displayLink(ListNode *head)
{
    ListNode *p;
    p = head;
    cout << "head-->";
    while (p != NULL)
    {
        cout << p->val << "-->";
        p = p->next;
    }
    cout << "tail\n";
}
int main()
{
    ListNode *head = createByTail();
    head = Solution().ZZZ(head);
    displayLink(head);
    return 0;
}